Four years ago, a little over three thousand people raised $72K on Kickstarter to make Six to Start’s Zombies, Run a post-apocalyptic reality. The smartphone app allowed runners to step into the role of Abel Township’s Runner 5, the largely silent protagonist collecting supplies for the town in a world infested with zombies. Three seasons and over 200 missions later, over a million people purchased the game, following its often heart-wrenching story as Runner 5 gradually gets to know the inhabitants of Abel Township, neighboring settlements, and the truth behind the zombie infestation. And now, with season 4, Zombies, Run has gone free-to-play.

One of the challenges that Zombies, Run faces is that while it’s an exceptionally intuitive game to pick up, it’s deceptively hard to describe to people who haven’t plugged in a pair of headphones and entered a new audio landscape. It’s easy to assume the game’s appeal is the thrill of the chase: the spike in adrenaline as the moans and groans of an undead horde interrupts an evening jog, and the dread realization that with every step, they’re getting closer. And while the zombie chases are a rush, it’s an optional feature in a game that focuses on a compelling narrative to convince its players to keep coming back out for more. It’s temptation bundling at work – a compelling narrative with fascinating characters you can only encounter while on the move. The ragtag band of survivors in Abel Township has inspired a vibrant fan community.

Zombies, Run‘s shift to the free-to-play model was intended to help make it easier for people to experience the game. As Zombies, Run co-creator and Six to Start CEO Adrian Hon explains,

[the game] has a great hook but a lot of people still think it’s just zombie groans and chases…unlike Monument Valley or 80 Days or Candy Crush, where you can understand the game from just a screenshot or video, Zombies, Run really requires people to try it out…going free-to-play helps people over that hurdle.

So now, players experiencing Zombies, Run for the first time receive access to the first four missions of season 1 right off the bat. Once a week, they have the ability to unlock a new mission to add to their growing repertoire. As a thank you to returning players, anyone who previously purchased a copy of Zombies, Run receives the first three seasons for free, and can use their weekly mission downloads to gradually claim the newest season as it’s released.

Six to Start hasn’t completely abandoned its subscription-based revenue streams: instead of offering season downloads for a flat fee, the game’s most ardent fans can sign up for monthly or yearly subscriptions ($2.99 a month or $19.99 a year) allowing them to unlock everything at once, along with additional running modes and statistics. By switching from flat-fee pricing for seasons to a subscription model, Hon hopes to provide support for the app, with a constant stream of new features in development as opposed to the game’s seasonal bursts. Six to Start has announced that one of these features in development is Apple Watch integration for the game.

However, the intent is to transition to hybrid revenue streams made possible by expanding the game’s current player base, numbering in the hundreds of thousands. As Hon explained to the Guardian, a wider audience would make alternate revenue streams like integrated audio advertisements, books, real-world events, and zombie races more feasible. Earlier versions of the app gave a hint at what one possibility of what advertising might look like. Chipotlelabs, one of the game’s early Kickstarter backers, popping up during certain item drops thanks to a $2,500 perk that allowed backers to name a brand. With the game’s focus on hunting down coveted supplies for the township, it’s all to easy to imagine a host of opportunities to integrate audio advertisements into the story without breaking the immersion. In Virtuous Circle, one of my favorite episodes from Zombies, Run‘s first season, Runner 5 is sent on a mission to raid the local hobby stores for the town’s most coveted recreational supplies.

Six to Start’s revenue models weren’t the only part of Zombies, Run to get an overhaul: the free-to-play app’s user interface has changed dramatically, tightening up the experience and making it even simpler to start playing. The game’s home screen prominently highlights the player’s next mission, while completed missions feature narrative summaries to remind players who haven’t gone out on a mission for a while.

While previously the music accompanying Zombies, Run was limited to playlists stored on the player’s phone, Zombies, Run now supports Pandora and Spotify playlists. Each mission comes with an estimate of how long it will take to complete, and as snippets of story are unlocked, a progress bar shows how far the player has to go before completing the mission. And while previously missions would automatically switch to “Radio Mode” featuring lighthearted banter between Jack and Eugene, players going on longer runs can now ask the game to skip to the next mission.

The most devilish update of all, however, was the addition of “Next on Zombies, Run” teasers. Every episode starts with an optional reminder of what happened on the last mission, and concludes with a tantalizing taste of what’s to come. These sensationalist samples have led me to binge-jog missions of Zombies, Run just like I normally binge-watch shows on Netflix. Players may have the option to treat Zombies, Run like a free weekly television series, but the “Next on Zombies, Run” teasers will make a yearly subscription to the service look quite tempting.

The shift to a freemium model for Zombies, Run is a risky one – while giving players who previously paid for the game full access to the first three seasons should ensure they aren’t put out at having to pay for something new players can receive for free, receiving one free episode a week also means that for casual players, a paid subscription is less of a necessity. For this strategy to work, the onus is on new players to give Zombies, Run a try, now that Six to Start has “raised the gates”, making Abel Township accessible to people not yet ready to pay for an audio adventure about the end of the world.